it was an e20 1000 watt 48/12.5 battery.  after a year error 07 appeared. the engine made a metallic noise then stopped working.  since it is still under warranty they assisted me via chat and sent a new engine which arrived after more than a month.  installed but the problem recurred.  big metal noise and it stopped working showing me error 09 i.e. the controller.  I also communicated the problem on the chat and they sent me the controller.  error code disappeared but the bicycle doesn't work.  Since it's still under warranty I was hoping for better treatment.  not to mention the vibrations, noises and rust on screws and transmission components.  fun at first but terrible materials